Master Cylinder Stroke Sensing With Nested Magnet Layout
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Solution Overview
Problem
The existing hydraulic braking apparatuses face challenges in ensuring signal accuracy for the stroke sensor due to a large air gap between the permanent magnet and the stroke sensor, which affects the magnetic field strength and subsequently the sensor's signal accuracy.
Innovation Solution
The hydraulic braking apparatus positions the permanent magnet inside the piston and the stroke sensor between the primary and secondary rubber cups, with a blind hole for protection, and includes an anti-rotation mechanism to prevent magnetic field changes caused by rotation, while ensuring the solenoid valve is at a sufficient distance from the stroke sensor to prevent magnetic flux interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the permanent magnet is positioned farther from the stroke sensor, then the magnetic field strength at the sensor is reduced, but the structural design becomes simpler and easier to manufacture
Solution Approach 1:
The permanent magnet is nested inside the piston cavity, and the stroke sensor is nested within the master cylinder assembly. This nested arrangement allows the magnet and sensor to be positioned in close proximity without requiring separate mounting structures, thereby ensuring strong magnetic field signal while maintaining structural simplicity and ease of manufacture.
Solution Approach 2:
The patent positions the permanent magnet inside the piston (radial dimension) rather than on the end face, and places the sensor within the master cylinder assembly. This dimensional repositioning reduces the air gap distance between the magnet and sensor, enhancing magnetic field strength while avoiding complex external mounting structures.
2Measurement precision
If the permanent magnet is placed close to the stroke sensor, then signal accuracy is improved, but the risk of magnetic flux interference from nearby components increases
Solution Approach 1:
The patent extracts the permanent magnet from the traditional position on the end face of the piston and relocates it inside the piston cavity. This separation removes the magnet from the interference zone of the solenoid valve's magnetic flux while maintaining close proximity to the stroke sensor, thereby ensuring signal accuracy without magnetic interference.
Solution Approach 2:
The piston structure serves as an intermediary barrier between the permanent magnet and the solenoid valve. By positioning the magnet inside the piston cavity and the sensor within the master cylinder assembly, the piston and surrounding structures act as magnetic shielding intermediaries that protect the sensor from external magnetic flux interference while allowing the magnet-sensor interaction to function properly.
3Measurement precision
If the permanent magnet is positioned inside the piston, then the air gap is reduced and signal accuracy is enhanced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent merges the permanent magnet positioning with the existing piston structure by placing the magnet inside the piston cavity. This integration utilizes the piston's existing manufacturing features and tolerances, avoiding the need for separate high-precision positioning structures. The magnet is secured using standard adhesive or mechanical retention methods that are consistent with conventional piston manufacturing capabilities.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces the air gap between the permanent magnet and the stroke sensor, enhancing signal accuracy and stability by minimizing magnetic flux leakage, thereby improving the overall performance of the braking system.
Implementation Method 1
the permanent magnet moves with the pushrod to make a magnetic field change at the stroke sensor, and the stroke sensor senses the change to output an electrical signal
Data Source
AI summary
A hydraulic braking apparatus includes a first hydraulic block; a master cylinder assembly, disposed in the first hydraulic block, where the master cylinder assembly includes a pushrod, a piston, a primary rubber cup of the piston, and a secondary rubber cup of the piston, and where the piston is connected to the pushrod; a permanent magnet is disposed inside the piston; and a stroke sensor is disposed between the primary rubber cup and the secondary rubber cup and configured to detect movement of the permanent magnet to determine an amount of movement of the piston.